Caption: Mycobacterium tuberculosis. Coloured Transmission Electron Micrograph (TEM) of a single bacterium, Mycobacterium tuberculosis. This is a Gram- positive rod-shaped bacillus bacterium that causes tuberculosis (TB) in humans. The outer surface of the cell is covered by a complex of proteins, fats & lipids. These surface proteins stimulate an immune response from an infected patient. Mycobacterium tuberculosis is spread by coughing or sneezing, and is inhaled into the lungs. It forms a primary tubercle during initial infection, which develops into pulmonary TB. TB is still a fatal disease in developing countries and among AIDS patients. Magnification:x24,000 at 6x7cm size. Magnification:85000 at 8x10' size.